Hi, I am looking at buying a 2002 A4 3.0 with 127,000 miles from an upscale new car dealer. The car looks and drives really nicely, but I noticed there was a light yellow foam on the oil filler cap after I drove the car for about 10 miles, the outside temperature was about 48 degrees.When I brought it to the attention of the salesman, he said he would have the mechanic look at it. I called him back later that day and he said the mechanic told him it's a common occurrence on these cars. Does anyone have experience with this issue? thanks